Distribution of dry matter and nitrogen between the different plant parts in intact and depodded soyabean plants after flowering.

Abstract

Soyabeans were grown in nutrient sol. in a controlled environment. 50% developed normally but the rest were depodded once a wk. During 9 wk of seed development, growth of roots, shoots, leaves and pods as well as their total percentage N was monitored by weekly harvests. In the normal plants, only the pods continued to increase in dry wt. after the 2nd harvest and the wt. of the other plant parts remained nearly constant. N in roots and stems decreased slightly during pod filling and N in the leaves decreased considerably. Increase in N in the pods was relatively greater than the increase in total dry wt. The amount of N taken up from the nutrient sol. and that redistributed between plant parts was calculated. In the depodded plants, DM continued to accumulate in all plant parts throughout the experiment including the detached pods. The amount of N also increased in all plant parts. N uptake/unit DM produced was about the same for both groups of plants. The results are discussed in relation to the hypothesis that in leguminous plants the fixation or uptake of N by the roots cannot cope with the demand of the developing pods so that the necessary withdrawal from other plants parts, especially the leaves, causes the plants to die prematurely. (Abstract retrieved from CAB Abstracts by CABI’s permission)